Device for the transmission of measurement values over long-distance lines



Sept. 3, SCHLElCHER 2,013,544

DEVICE FOR 'THE TRANSMISSIQN OF MEASUREMENT VALUES OVER LONG DISTANCE LINES Filed 001;- 24, 1929 AA A VVVVVYV Patented Sept.- 3, 1935 UNETED s'ra'rss DEVICE FOR TilE TRANSMISSION OF MEAS- UREMENT VALUES OVER LONG-DISTANCE LINES Manfred Schlcicher, Berlin-Charlottenburg, Germany, assignor to Siemens & Halske, Aktiengesellschaft. Sicmcnsstadt, near Berlin, a corporation of Germany Application October 24, 1929, Serial No. 402,230 In Germany October 31, 1928 3 Claims. (c1.177 s51) My invention relates to improvements in devices for the transmission of measurement values over long-distance lines.

In the transmission of suchvalues over long distances. for instance from a.substation to a main station at a considerable distance away, it is already known to send impulses from the measuring station the frequency-of which in the unit of time corresponds with the measurement value to be transmitted, It has also been proposed to employ direct current impulses for the transmission. This is, however, difficult if not impossible if repeaters are connected in the transmission lines. Telephone lines which in order to avoid risks from high potentials must contain at least two repeaters can therefore not be utilized for remote measurements. Another proposal is to employ high frequency impulses. A special high frequency generator is then necessary at the transmitting station and filter chains at the receiving station for separating the high frequency impulses from the service frequency.

The object of my invention is to provide an improved device operating without the aid of a high frequency generator and which enables the transmission of the impulses over existing service telephone lines.

In my improved device the transmitter energy is taken from the mains through a frequency transformer. The transmission takes place, at a frequency which corresponds with the second harmonic of the service frequency. Impulses of this frequency are able to pass over the telephone lines and through the repeaters connected in the line without any difliculty.

In the main and receiving station arelay is actuated by the arriving impulses and causes a condenser to be charged and discharged at a frequency corresponding with the arriving inrpulses. A sluggish measuring instrument indicates the average value of the charging and discharging current of the condenser.

My improved device has the advantage over apparatus working with high frequency impulses that no high frequency generator is necessary. The change of frequency may be effected by a. stationary telephone frequency changer which requires no care and attention. My improved device has a greatly extended sphere of application as the impulses cannot be stopped by repeaters connected in the line, as happens in apparatus employing direct current impulses. There are no objections to the use of impulses which correspond to double the frequency of the mains, because if impulses of the easily produced double frequency of the mains are used for the transmission the power current lines are not affected at all.

An embodiment of my invention is illustrated in the drawing affixed to my specification.

Referring to the single figure of the drawing I is an alternating current generator feeding two busbars 2 and 3. The output of the generator I is to be indicated at a remote control station and for the transmission of the value measured an arrangement is to be employed which dispatches impulses the frequency of which corresponds with the frequency of the output of the generator I. The transmission impulses are derived from a source of alternating current which consists of a frequency converter connected to the busbars 2, 3.

' The output of the generator I is measured by a Ferraris electricity meter 4 which is provided with a current coil and a potential coil 6. The current coil 5 is connected to a current transformer l which is excited by the current from the generator I. The potential coil 6 is connected to the secondary winding of a potential transformer 3 which is excited by the busbar voltage. The Ferraris meter is also equipped with a brake magnet 9, which brakes its disc ID in such a manner that its-speed is proportional to the output of the generator I. On the spindle I I of the Ferraris meter 4 is mounted a collector I2 upon which rest two sliding springs I3 and I4. During the rotation of the spindle I electric connection is periodicallymade and broken again between the sliding springs I 3 and Id. The sliding springs I3 and I4 are connected in a circuit which contains a secondary coil I5 of an intermediate transformer I6 and one coil of a repeater I I in the long distance line. The intermediate transformer I6 is excited by the coil I8 through which passes a current impulse through two rectifiers I9 and 20 during each semi-wave of the alternating voltage of the generator I. The frequency of the excitation of the coil I8 is thus double the service frequency of the alternating current plant 2, 3. Everytime the sliding springs I3 and I4 are connected with each other through the col- I lector I2, there is transmitted to the repeater I? an alternating current impulse which has a frenquency which is double the service frequency of the power current line. These impulses are transmitted to the receiving station through the said repeater I1 and a further repeater 2| and there energize a relay 22. When this relay 22 is energized it closes a contact 23 and thus energizes a relay 24. The relay 24 controls in well known manner a change-over switch 25 by which the poles of a condenser 26 are changed over. The condenser is during each excitation of the relay 24 charged by a current impulse from a battery 21. The mean value of these charging currents is indicated by an indicating instrument 28. The deflection of this indicating instrument thus depends on the speed of rotation of the meter 4 and consequently also on the value of the power out put of the generator I It will be noted that the frequency-converter l6 illustrated herein is of the stationary type, that is, it has no movable parts. I prefer to use this type of frequencyconverter on account of various advantages it ofiers, particularly as it is not subject to wear, such as is unavoidable when a converter having movable parts is employed.

Apart from the transmission of the measurement values the long distance transmission lines also serve for the telephonic communication between that station in which is located the generator l and the meter 4 and the control station where the measuring instrument 28 is mounted. The telephones 29 and 30 are connected to the long distance lines through filter chains 3! and 32. These filter chains keep the actions of currents induced on the telephone lines by the power lines away from the telephone apparatus.

The relay 22 at the control station is either sensitive for alternating currents of that frequency only which is employed for the transthe frequency of the mains, means for controlling the currents produced by said converter, in dependence on the measurement to be transmitted, a line to receive and transmit the impulses which are produced from the said double frequency currents with the aid of said controlling means, whereby said line will not be affected by surges in the alternating current in said mains, and a measuring instrument responsive to said transmitted impulses.

2. In a device for the transmission of measurement values, by means of electric impulses the number of which per unit of time corresponds to the measurement to be transmitted, alternating current-distributing mains, a frequency converter energized by said mains and constructed to producealternating currents having double the frequency of the mains, a circuit-breaker by which said double frequency currents are broken upon into impulses, means for operating said circuit-breaker in dependence on the measurement to be transmitted, a line to receive and transmit the double frequency impulses produced with the aid of said circuit-breaker, whereby said line will not be affected by surges in the alternating current in said mains, and a measuring instrument responsive to said transmitted impulses.

3. In a device for the transmission of measurement values, by means of alternating current impulses the'number of which per unit of time corresponds to the measurement to be trans mitted, alternating current distributing mains, a frequency converter energized by said mains and constructed to produce alternating, currents hav- MANFRED SCHLEICHER. 

